post-trial access cohort BUmetanide for Developmental DIsorders

Child psychiatric neurodevelopmental disorders (Attention Deficit Hyperactivity
Disorder (ADHD), autism spectrum disorder (ASD), intellectual disability and
learning disorders) are highly heterogeneous conditions affecting the daily
lives of about 1 in 10 children worldwide. Especially the more severe case
require medical intervention but current medicinal interventions are at best
symptomatic and do not target pathophysiological mechanisms.
Despite extensive clinical variability, experimental research has indicated
common pathways and treatment targets across neurodevelopmental disorders. For
example, bumetanide, used for decades as a diuretic drug, has recently been put
forward as a rational, safe off-patent intervention to improve GABAergic
inhibition across neurodevelopmental disorders (NDDs). Several successful
trials in the field have led to the approval of an EMA pediatric investigation
plan for bumetanide for ASD and a phase III trial is underway
(https://clinicaltrials.gov/ct2/show/NCT03715153).
Recently, we have conducted three independent trial studies testing bumetanide
across the spectrum of NDDs. Our overall hypothesis was that bumetanide
improves the balance between excitation and inhibition (E/I) with effects on
sensory and cognitive information processing that in turn may improve core
behavioral symptoms. Indeed, neural excitability and sensory processing is
increasingly being marked as one of the fundamental processes underlying NDDs.

Consistent with our hypotheses, we found that bumetanide and not placebo alters
the E/I balance (EEG biomarkers) and improves core symptomatology of NDDs in a
substantial subset of patients. However, the extent and type of response was
variable between individuals also within the same diagnostic subcategory.
Another important lesson was that some of the effects reported by participants
were not represented by the clinical endpoint questionnaires.

As a result, many patients and caregivers that participated in our trials are
very eager to make use of the post-trial access to bumetanide treatment as
described in the original protocols. Indeed, if we do not administer
bumetanide under well-controlled circumstances, parents will seek alternative
providers with the risk that random *one-size-fits-all* off-label prescription
will become standard for bumetanide. In addition, we want to collect biobank
samples (blood and skin biopsies) to be able to perform genetic and cellular
analyses to develop additional stratification markers for future more
personalized application of the drug.

Thus, we propose a protocol for off-label bumetanide treatment to participants
of the previous trials. The duration of treatment will be a minimum a
six-months period and a maximum a two-year period. Reasons to mark this
post-trial access cohort (i.e. delayed open-label extension phase) as research,
for which we seek this IRB approval, and not as regular evidence-based clinical
care, are:
• off-label bumetanide treatment is still considered experimental
• no rational alternatives exist for any NDDs
• benefit of bumetanide has been suggested in multiple state-of-the-art RCTs
• Patients and caregivers will seek other prescribers of bumetanide if
post-trial access is not arranged by us.

Our aim is to confirm previous found effects of bumetanide on NDDs and to
identify markers allowing us to estimate individual treatment response. Given
that the end points previously used appeared non-representative of the effects
observed by participants* caregivers we will use a different primary endpoint.
This is also why we allow all participants of our previous trials access to
this open label extension cohort, even if previous data suggests there might
not be an effect. Furthermore, it is not yet known whether a longer treatment
duration might have added effects, which can also be a reason for participants
labeled as *non-responders* to participate in this trial. Patients and their
caregivers have received an information letter about the group they were
allocated in and whether they were grouped as responders/non-responders
allowing them to make an informed decision whether to, or not to participate in
this open-label trial.

Many trials focus on a one-size fits all treatment, leading to individual
comparison to the mean. However, the large heterogeneity of NDDs suggests this
might not be sufficient. A notion that is supported by our BAMBI data, where
subgroups of responders and non-responders could be identified. Accordingly, we
propose to use a more individualized study design, where the patient serves as
its own control.

We aim to estimate individual treatment response by using single-case
experimental designs (SCEDs). A SCED is an N-of-1 design in which a baseline
period is compared to an intervention period, evidence of treatment effect is
based on demonstrating that the change in behavior only occurs during
intervention. As the individual serves as his or her own control in this
design, the response per individual can be analyzed. To assess treatment-effect
a frequent measurement of target behavior is required. Therefore, we use a set
of person-centered measures that evaluates and monitors physical, mental, and
social health in adults and children: *Patient-Reported Outcomes Measurement
Information System* (PROMIS).

By simultaneously performing rsEEGs, neurocognitive testing and collect blood-
and skin biopsies with these 'patient reported outcome measures* (PROMs) we aim
to develop prognostic markers for treatment effect. To gain inside how PROMs
relate to the conventional endpoint measurements we also incorporate the
conventional questionnaires as secondary outcome measures.

1. Provide post-trial access to bumetanide treatment for NDD participants.
2. To test how bumetanide cohort data compare to the existing RCT data in terms
of treatment effectiveness by using randomization tests.
3. To further develop EEG biomarker treatment-effect predictions.
4. To establish a biobank of blood and skin biopsies for future additional
predictive biomarker development.

Post-trial access cohort (i.e. delayed open-label extension phase) over a
time-period for a minimum of a six-months period and a maximum of a two-year
period. Executed in a moncenter study of multiple n-of1 trials using
Single-Case Experimental Designs (SCEDs) testing bumetanide treatment during
six months with the primary end point of change in PROMs at Day 180 in
approximately 75 children with NDDs between 8 and 20 years of age. The effects
on PROMs will be compared to the main conventional endpoints used in the
original trials as well as accompanying measurements of EEG and neurocognition
to further establish effects on brain activity and functioning and to validate
predictive markers of treatment response.

Bumetanide 2dd1.0-2.0mg daily.

Nature and extent of the burden and risks associated with participation,
benefit and group relatedness:
The burden and risk of the application of this off-label drug for children with
NDD are acceptable while the benefits are expected to be considerable
especially when taking into account the lack of treatments for these highly
prevalent and often devastating disorders.

Risks
Bumetanide has been used as a diuretic drug for decades. In patients with
conditions of fluid overload, its safety and tolerability after short and
prolonged treatment has been established in all ages apart from neonates.
Experience and safety of bumetanide in patients with NDD is based upon recent
studies, including three randomized controlled trials in a sample of 56, 92 and
83 children7. These data indicate that bumetanide significantly alleviates
behavioral morbidity at dosages ranging from 1 to 2 mg daily. The main observed
adverse events were related to the diuretic activity of the molecule leading to
a decrease in electrolytes, notably mild hypokalemia, are frequently reported.

Skin biopsy is a safe, commonly performed procedure, carried out by a
healthcare professional. The risk of this procedure includes transient
bleeding, which usually subsides within minutes. There is a minimal risk of
wound infection and/or prolonged discomfort to the patient. If technological
advances will make it possible to use in the future alternative sources of
patient cells, such as hair, buccal or blood cells, this will be implemented in
the study to minimize the risk and discomfort of the patients further.

Burden
The main burden of this study is posed by the outpatient clinic visits to
follow up the safety of the diuretic effects. This requires physical
examination and blood tests, which are of negligible and known risks.
Additional burden is posed by the measurement of cognitive and EEG tests. These
tests are deemed necessary to further develop the prognostic markers to select
the most responsive patients out of the NDD population.

Skin biopsies are not commonly carried out as part of the diagnostic or
treatment procedures and will optionally be performed specifically for the
purpose of this study (unless a sample of fibroblast cells is available
already). By obtaining a skin biopsy from patients it will be possible to
create a cellular model, without interference of unknown modulating factors in
the patient*s genome, to perform cellular analyses in order to develop
additional stratification markers.

Benefit and group-relatedness
The promising results of our previous bumetanide trial studies are here
followed up in order to confirm and specify efficacy on symptomatology
important for the individual patient and to establish prognostic EEG markers
that can predict favorable effects in patients with NDD.